Liquid dispensers which employ a wick to convey a liquid or a volatile material from a container to a emanator, are well known in the art. A wide variety of liquid dispensers which are designed to slowly diffuse an active liquid, and which employ a wick, already exist. The active liquid may be a volatile scent-producing liquid, as in the case of air fresheners. In the case of wick type air fresheners, the scent-producing liquid is conveyed from a container, by means of capillary action through a wick, to an emanator, which diffuses the scent-producing liquid into the atmosphere in the form of a vapor, by the process of evaporation. Wick type liquid dispensers, which diffuse an active liquid material into the atmosphere, at a slow controlled rate, are not limited to use as air freshening devices. The active liquid in wick type slow release dispensing devices, may be chosen as a suitable composition for the use as a deodorizer, insecticide, pesticide, insect repellant, animal repellant, animal attractant, and the like. Another use for wick type liquid dispensers is to deliver a liquid pharmaceutical composition from a liquid container, through a wick, to an emanator in contact with the skin, whereby the pharmaceutical composition is slowly delivered and absorbed transdermally into a living body. A further use for wick type liquid dispensers is to deliver liquid nutrients or fungicides to vegetative soil or into the water of hydroponic vegetative cultivations. The examples of wick type dispensing devices mentioned above, all have a common desirable requirement to provide a slow controlled delivery of an active liquid over an extended period of time, through the use of a wick. While wick type liquid dispensing devices are applicable to many different uses with minor modifications, wick type liquid dispensers are especially suited, and commonly used for air freshening devices, thus the prior art is described in particular detail in reference to the use as an air freshener.
Many varieties of wick type dispensers are well known in the art of air freshening devices. Air freshening devices are useful for the purpose of dispensing and diffusing a volatile scent-producing liquid into the atmosphere of homes, public areas, offices, transportation vehicles, and other areas which may exhibit objectionable odors. The scent producing liquid in wick type air fresheners may be available in a variety of different fragrances to treat or mask objectionable odors and provide a long lasting pleasant odor. In order to be effective, the wick type dispensing device must provide the desired fragrance at a slow uniform rate, over an extended period of time. The air freshener would be uneconomical if it would not last long and require frequent replacement. Another problem with prior art wick type air fresheners, is an initial delivery of a large amount of fragrance, and then subsequently a delivery of progressively less fragrance. The initial large dose of fragrance can be objectionable and even cause headaches in certain people, while the subsequent depleted fragrance produces a small dose of fragrance inadequate for the intended objective.
The most basic wick type air freshener is comprised of an absorbent material, impregnated with a scent-producing volatile liquid. The absorbent material acts as the liquid container, wick, and emanator all combined. The scent-producing fragrance is absorbed into the absorbent material by capillary action. The fragrance impregnated absorbent is commonly packaged in a non-permeable wrapper or container to prevent the evaporation of the scent producing liquid into atmosphere, before its intended use. Examples of absorbing material used in prior art are; blotter paper, felt, cellulose, cotton, wood chips, dried vegetation, sponge material, and other porous or fibrous material. The absorbent is commonly shaped or presented in an attractive or decorative manner. The primary disadvantage of the absorbent type of air freshener is its inability to deliver a slow controlled amount of fragrance to the atmosphere. The absorbent type of air fresheners, release a concentrated dose of fragrance quickly when first activated, then over a relatively short period of time the perceived fragrance intensity becomes inadequate in its ability to provide a pleasant fragrance to the atmosphere.
The rate of fragrance evaporation to the atmosphere by the absorbent type of air fresheners, is controlled to a great degree by its exposed surface area and ambient temperature. A large exposed surface area would provide a greater rate of fragrance evaporation. Variations in ambient temperatures also would produce variations in fragrance diffusion rate into the atmosphere. Many of the absorbent type of air fresheners are commonly used inside of transportation vehicles. A disadvantage in the use of this type of air freshener for use in vehicles, is caused by temperature variations commonly encountered in a vehicle. If the vehicle is parked with its windows closed on a hot sunny day, the greenhouse effect of the sun and windows may produce extremely elevated temperature within the vehicle. The elevated temperature will accelerate the evaporation rate of fragrance in an absorbent type of air freshener, to produce an objectionable strong scent in the vehicle. A further disadvantage of the absorbent type of air freshener is the limited volume of the scent-producing liquid, dependent upon the absorption capacity of the absorbent material. Another further disadvantage of the absorbent type of air freshener is the requirement of the relatively large exposed surface area of the absorbent in contact with the atmosphere. A large area of scent-producing liquid in contact with the atmosphere is undesirable, because the absorbent emanator permits a large interface area between the scent-producing liquid and atmospheric oxygen, which can degrade liquid fragrances, thus producing undesirable fragrances.
Many improvements to absorbent type of air fresheners have been devised, to provide increased control over the diffusion of the scent-producing liquid into the atmosphere. One such improvement involves the use of apertures, or more specifically the control of the aperture size of a container, which houses an absorbent, impregnated with a scent-producing liquid. Increasing the effective size of the housing apertures, will increase the rate of scent vapor evaporated into the atmosphere. Conversely, decreasing the effective size of the apertures, will decrease the rate of scent vapor evaporated into the atmosphere. As an example, U.S. Pat. No. 4,549,693 to Barlics et al., discloses a dispenser, comprised of a two part circular housing, containing a round absorbent pad, whereby the effective aperture openings in the housing are controlled by an up and down sliding motion, bringing the apertures in each part, in and out of register. U.S. Pat. No. 4,306,679 to Dusek et al., discloses a dispenser with a two part housing, containing a round absorbent pad, whereby the effective aperture openings in the housing are controlled by a twisting motion, bringing the apertures in each part, in and out of register. A further attempt to control the rate of diffusion in an absorbent type of air freshener, is disclosed in U.S. Pat. No. 4,280,649 to Montealegre. The aperture control in this patent consists of a two part rectangular carton, sliding up and down to provide a means to vary the aperture size. U.S. Pat. No. 4,712,737 to Hecking, discloses another method to control the aperture size in an air freshener housing, by the use of release tape to uncover a plurality of apertures. All of the above patents describe a method to control the rate of diffusion of a scent-producing liquid into the atmosphere, by control of the aperture size in the air freshener container. A basic disadvantage associated with the above patents is the requirement for a user to continually adjust the housing aperture to maintain a desired scent level. A further disadvantage is the limited supply of scent-producing liquid, which is dependent upon the liquid absorbing capabilities of the absorbent.
Improvements to the scent-producing liquid capacity have been made, through the use of two compartment or multicompartment containers, for absorbent type air fresheners. An example of such an improvement is disclosed in U.S. Pat. No. 4,998,671 to Leifheit, whereby the dispenser is comprised of a two compartment flexible bag. The scent-producing fluid compartment is maintained isolated from the absorbent, until time of use. At the time of use, a rupturable barrier is broken, providing a passage from the scent-producing liquid reservoir to the absorbent emanator. The emanator is maintained impregnated with the scent-producing liquid. U.S. Pat. No. 4,762,275 to Herbert et al., discloses a flat rigid container, maintained separated from an absorbent emanator by a puncturable membrane. At the time of use, a pointed element pierces the performable liquid reservoir, providing a passage for the active liquid to maintain the absorbent emanator continuously impregnated. The air freshener dispenser disclosed in U.S. Pat. No. 4,330,079 to Sato et al., discloses a scent-producing liquid reservoir, which is maintained isolated from an absorbent emanator pad until the time of use. At the time of use, a pointed element pierces a rupturable membrane to allow passage of the scent-producing liquid from the reservoir to the absorbent and maintain the absorbent emanator impregnated with the active liquid. A rotary control is also included on the housing, over the emanator pad to control the scent vapor evaporation rate, by varying the register between apertures with a rotary wheel. A disadvantage of the patents disclosed above is their inability to adequately control the amount of scent-producing liquid to the absorbent emanator. The absorbent emanator is maintained saturated with liquid thus producing a high concentration of fragrance vapor. U.S. Pat. No. 4,339,079 also attempts to address this disadvantage through the use of a variable aperture window. Aperture control would be time consuming to a user, requiring constant attention to aperture regulation to maintain a desired fragrance level. A further disadvantage is a result of the relatively large surface area of active liquid, impregnated in the absorbent, in contact with atmosphere oxygen. Degradation by oxygen, of the fragrance over time, may produce undesirable odors.
Numerous modifications to the basic wick in a bottle type of air freshener have also been devised, in an attempt to extend the useful life of a scent dispenser, improve control over the rate of fragrance diffusion, and spill prevention of the scent-producing liquid. In its basic form, a wick in a bottle air freshener consists of a narrow neck bottle container holding the scent-producing liquid, whereby a wick is raised out of the bottle, in contact with the atmosphere at one end, and in contact with the liquid at the other end. Prior to use, the wick is contained within the bottle allowing a cap to seal the bottle and prevent spillage of the scent-producing liquid. An advantage of the bottle container, is in its capacity to hold a relatively large amount of scent-producing liquid, resulting in a prolonged useful life of the dispenser. An example of a wick in the bottle air freshener is disclosed in U.S. Pat. No. 3,091,396 to Curtin. This patent discloses a rigid framework on the wick, to provide a convenient means of varying the scent evaporation rate, by raising and lowering the wick, resulting in a control over the evaporative surface area of the dispenser. Improvements in prevention of potential spillage, of the scent-producing liquid are disclosed in U.S. Pat. Nos.; 4,742,960 to Bustillo et al., 3,724,756 to Maltenfort, 3,207,441 to Schreiber, 3,091,396 to Curtin, and 3,028,100 to Xenakis et al. While the improvements disclosed in the above patents have been found useful, the wick in the bottle type of air freshener does not provide an adequate control, to deliver a scent-producing liquid at a slow constant rate over an extended period of time. Numerous time consuming adjustments and attention must be provided, in an attempt to maintain a desirable fragrance level in the atmosphere. U.S. Pat. No. 4,323,193 to Compton et al., is a further attempt to control the diffusion rate of the scent-producing liquid into the atmosphere at a slow steady rate. The wick is in the form of a sheet, surrounded by a container, with adjustable aperture slots. Constant attention must be provided to adjusting the apertures, to maintain a desirable scent level. A further disadvantage of wick in the bottle dispensers, is the relatively large liquid saturated surface area in contact with the oxygen in the atmosphere. Oxygen can combine with the active liquid, producing undesirable degradation products.
Attempts to provide a slow controlled rate of diffusion by a scent-producing liquid in the atmosphere, have been made by dispensers comprised of; a sealed container holding a scent-producing liquid, a wick to convey the active liquid to an emanator, and an absorbent emanator to provide an evaporative surface area for the liquid diffusion into the atmosphere. U.S. Pat. No. 4,928,881 to Barlics et al., discloses an air freshener with a vented, liquid sealed container for the scent-producing liquid. This patent also describes a wick continuous with an absorbent diffuser pad. The wick is positioned internal to the container and in contact with the scent-producing liquid. The absorbent emanator is positioned on top of the liquid container. A decorative cover provides an aperture in an attempt to control the rate of scent evaporation. Many additional modifications have been devised in an attempt to control the rate of scent diffusion. U.S. Pat. No. 5,014,913 to Hoyt et al., discloses a hinged two part shell cover surrounding the dispenser. An attempt to control the rate of the liquid diffusion is made, by requiring the user to open or close the wings of the shell. U.S. Pat. No. 4,739,928 to O'Neil, discloses an air freshener with a liquid container, wick, emanator pad, and an adjustable aperture cover to control the rate of diffusion. Rotating the cover brings the apertures in and out of register, thereby controlling the diffusion of the scent vapor. U.S. Pat. No. 4,419,326 to Santini, discloses the use of internal rigid porous wicks to regulate the rate of fluid transport to a porous plastic emanator. U.S. Pat. No. 4,915,301 to Munteanu, discloses an improvement over the previously mentioned patent, by the addition of a vent passage. U.S. Pat. No. 4,878,615 to Losi, discloses an air freshener device which requires pumping of an elastic membrane on the liquid reservoir container to replenish an absorbent emanator with scent-producing liquid. The disadvantage of this method is the time consuming attention, required of a user, to maintain a desired scent level. While the inventions disclosed above have been useful in some instances, their use to adequately control the slow constant diffusion of a scent-producing liquid into the atmosphere, are still subject to certain disadvantages. While the use of a sealed rigid liquid container has reduced the problem of liquid spillage, a vent passage from the atmosphere to the head space of the liquid container would be required. If the air freshener dispenser is accidentally knocked on its side, the vent passage could become blocked with the liquid inside the container, or if the vent is large enough, the liquid could slowly leak out of the dispenser. A blocked vent in a sealed dispensing liquid container would result in an increasingly slow dispensing rate and ultimately cease. The above mentioned air freshener devices, generally operate with the absorbent emanators saturated with scent-producing liquid. The relatively large surface area saturated with the scent-producing liquid, provides a large interface area with oxygen from the atmosphere. Atmospheric oxygen may degrade the liquid into compositions producing an undesirable scent. Many air fresheners require the scent-producing liquid to be diluted with another liquid which does not provide a scent. The diluted composition is required for dispensers with relatively large liquid saturated emanators, or an undesirable strong scent would diffuse into the atmosphere. The diluted scent producing liquid requires a relatively large container and precludes the use of a small compact liquid container, containing a concentrated scent-producing liquid. The inventions described above are also limited to placement on only horizontal surfaces, due to the shape of the liquid container. In certain applications, it may be more desirable to mount an air freshener on a vertical wall. A further disadvantage is the control of liquid diffusion, by time consuming attention, required to adjust the apertures on the dispenser.
The use of porous containers and microporous plastic membranes, permeable to the scent vapor but impermeable to the scent-producing liquid, have been used in an attempt to control the rate of diffusion of the liquid into the atmosphere as a vapor, in air fresheners. U.S. Pat. Nos. 4,948,047 to Zembrodt, and 4,634,614 to Holzner describes the use of a microporous plastic membrane to control the diffusion rate of a scent-producing liquid into the atmosphere. A further modification is described in U.S. Pat. No. 4,753,389 to Davis. The scent-producing liquid is stored in an absorbent material, inside a sealed container with a vapor plenum cavity which is sealed by a vapor permeable cap. The cap orifice area and the vapor permeable barrier, control the diffusion rate of the scent-producing liquid. U.S. Pat. No. 4,614,299 to Loveren et al., describes a dispenser comprised of a flexible microporous plastic inner pouch surrounded by a vapor impermeable outer pouch for storage. The inner pouch also contains a scent-producing liquid in the form of a gel. The diffusion of scent-producing gel is controlled by the vapor permeable properties of the plastic pouch. Porous ceramic containers have also been used to contain the scent-producing liquid, while allowing the scent vapors to diffuse through the container wall. A disadvantage common to air fresheners using a vapor permeable membrane or vapor permeable container to control the rate of scent diffusion, is their susceptibility to pore blockage and scent composition fractionating. The pores of the microporous container can become blocked if the air freshener is knocked on its side allowing the scent-producing liquid to coat the vapor permeable pores of the material. The scent-producing liquid may also be subjected to composition fractionating by vapor diffusion through the micropores. The most volatile vapors will pass through the micropores first, and subsequently the least volatile vapors of the fragrance composition will be diffused into the atmosphere last, resulting in a distortion of the scent over time.
The point made by these examples of prior art is, that while these liquid dispensing devices are somewhat satisfactory in some circumstances, the prior art devices are limited by the aforementioned disadvantages, thus there remains a need for an improved liquid dispensing device, capable of slow controlled dispensing and diffusion of liquids and vaporizable materials.